1. Field of the Invention
The invention relates to the field of measuring and testing instruments. More particularly, the invention relates to the field of liquid sample handling in measuring and testing instruments. In still greater particularity, the invention is a liquid transfer valve which is utilized with one or more movable probes. By way of further characterization but not by way of limitation thereto, the invention is a valve having a movable portion and a stationary portion which, in one position, allows the movable probes to access a substance and, in a second position, allows the substance to be ejected from the probe, combined with diluent in a fixed ratio, and delivered to a remote location.
2. Description of the Related Art
Measuring and testing instruments utilizing automated sample handling devices may be complex to build and operate when a number of liquids are to be moved to various locations. These instruments normally require that a sample fluid be diluted with a second fluid and/or reagent before being subjected to testing. This dilution must be accomplished quickly in order to allow a large number of samples to be tested. It may also be desirable to introduce calibration standards into the system at various time intervals. In addition, while washing of the probe is necessary to prevent contamination of subsequent sample liquids, this washing should be accomplished quickly and easily. To minimize the time required to complete these functions it is desirable to minimize the amount of system movement required.
Prior devices such as that shown in U.S. Pat. No. 3,747,412 issued to A. R. Jones on July 24, 1973 employ valves which include sections movable with respect to one another. The apparatus described in the above referenced U.S. patent is a trapped volume device in which the probe is connected to a movable valve portion. A sample liquid is drawn through the probe and into the valve where a predetermined volume of the sample liquid is trapped. The sample liquid is combined with a fixed volume of another liquid after movement of the valve portions which align conduits connected to sources of these other liquids. While suited for its intended purpose, this device does not allow probe movement with respect to the valves and washing of the probe must be accomplished in a separate step. In addition, the device is complicated and requires much supporting hardware.